Coatings which cure rapidly on exposure to ultraviolet light are well known, but these are usually poorly adherent to metal and plastic surfaces. Chromium surfaces are particularly difficult to adhere to. The vacuum deposited chromium surfaces require overcoating to protect them, and this is now done with thermally cured coatings. The purpose is to protect the metal surface from abrasion and moisture, as is encountered on exterior exposure. This is now carried out using a two-package system in which an hydroxy functional polymer and an organic polyisocyanate are mixed and applied and then reacted at moderate temperature to form a polyurethane coating. Adhesion to the chromium surface is less than satisfactory than desired, and the cure is slow.
This invention is directed to providing liquid ultraviolet-curable coating compositions which will cure rapidly to form a strongly adherent coating on metal and plastic surfaces, including vacuum deposited chromium, and which will protect these surfaces against abrasion, moisture and organic solvents.